1. Field of the Invention
This invention relates to a rear discharge mower unit for rearwardly discharging grass clippings cut by blades. The invention relates also to a lawn tractor having such a rear discharge mower unit suspended between front and rear wheels, and a grass catcher disposed rearwardly of the rear wheels.
2. Description of the Related Art
A rear discharge mower unit has a plurality of blades arranged sideways and rotatably supported in a mower housing, and rearwardly discharges grass clippings cut by the blades as entrained by air flows produced by the rotating blades. U.S. Pat. No. 3,469,376, for example, discloses a rear discharge mower unit having four blades arranged symmetrically sideways. The two left blades are rotatable clockwise while the two right blades are rotatable counterclockwise. Thus, all grass clippings are once collected in a middle region, and then thrown rearward through a space between the two middle blades.
U.S. Pat. No. 4,916,887 discloses a rear discharge mower unit having a side blade disposed at each opposite side of a center blade, and a mulching rotary blade disposed between the center blade and right side blade. The left side blade and center blade are both rotatable clockwise, whereby grass clippings cut by these two blades are fed confluently to a region to the left of the mulching rotary blade. Grass clippings cut by the right side blade are fed to a region to the right of the mulching rotary blade. The grass clippings are discharged rearwardly after being cut to pieces by the mulching rotary blade.
The former rear discharge mower unit has only a small space between the mower housing and each blade, and no special path provided for passage of grass clippings. Thus, the grass clippings cut by the blades cannot flow smoothly to the outlet, but tend to stagnate locally before discharge through the outlet. It is difficult to avoid the inconvenience of the grass clippings dropping from stagnating positions.
In the latter rear discharge mower unit, all the blades are rotatable in the same direction, which requires a relatively large distance between the path of grass clippings sent to the outlet by the center blade and the path of grass clippings sent to the outlet by the right side blade. This is obstructive to compactness of the mower housing.
A primary object of this invention is to solve the problems of the above conventional rear discharge mower units, and provide a rear discharge mower unit defining flow paths in a compact mower housing for permitting grass clippings to flow smoothly.
A secondary object of this invention is to provide a lawn tractor equipped with the above rear discharge mower unit of this invention, which includes no element projecting transversely of the tractor for transporting grass clippings from an outlet of the rear discharge mower unit to a grass catcher.
The primary object of this invention noted above is fulfilled by a rear discharge mower unit comprising a mower housing, a first side blade, a center blade and a second side blade arranged sideways in and rotatably supported by the mower housing, a power transmission mechanism for rotating the center blade and the second side blade in one direction and the first side blade in the other direction, a grass clippings outlet formed in a boundary region between the first side blade and the center blade, a center baffle extending around a rotational axis of the center blade and defining a center flow path for feeding grass clippings to the grass clippings outlet, a first side baffle extending around a rotational axis of the first side blade and defining a first side flow path for feeding grass clippings to the grass clippings outlet, and a second side baffle extending around a rotational axis of the second side blade and defining a second side flow path for feeding grass clippings to the center flow path.
In this construction, grass clippings cut by the second side blade flow through the second side flow path into the center flow path, and join grass clippings cut by the center blade. Further, the grass clippings are fed into the grass clippings outlet and join grass clippings cut by the first side blade and flowing in from the first side flow path. Thus, the grass clippings cut by the respective blades flow through the flow paths defined by the baffles to enter the grass clippings outlet reliably and smoothly. Then, the grass clippings may be discharged outside the mower unit or may be transmitted to a grass catcher through a duct. That is, the grass clippings may be discharged reliably to a predetermined position instead of being scattered in all directions.
In one preferred embodiment of this invention, the grass clippings outlet includes a discharge baffle connected to the center baffle and the first side baffle, the discharge baffle defining a discharge flow path for collecting and discharging grass clippings cut by the first side blade, the center blade and the second side blade. According to this construction, the center flow path and first side flow path are connected smoothly to the discharge flow path. Consequently, the grass clippings cut by the first side blade, center blade and second side blade flow into the discharge flow path without stagnating.
Where the discharge baffle includes a first baffle plate disposed adjacent the first side blade, and a second baffle plate disposed adjacent the center blade, the second baffle plate may extend obliquely to locate a discharge opening of the discharge flow path adjacent a middle position of the mower housing. Alternatively, the second baffle plate may extend linearly to locate the discharge opening of the discharge flow path away from the middle position of the mower housing. The location of the discharge opening may be selected according to the use of a lawn tractor on which the mower unit is mounted.
In a preferred embodiment of the invention, the second side flow path joins the center flow path in a region extending along a common tangent to circles of loci of the center blade and the second side blade, and the center flow path and the first side flow path join in a region extending along a common tangent to circles of loci of the center blade and the first side blade and communicating with the discharge flow path. In this construction, the grass clippings having flowed through the curved second side flow path flow along the common tangent toward the center flow path curved likewise. Thus, the grass clippings flow smoothly without being unnecessarily decelerated. Further, the grass clippings having flowed through the curved center flow path and first side flow path flow along the common tangent into the discharge flow path lying ahead, without being unnecessarily decelerated. This construction contributes to smoother flows to the discharge flow path of the grass clippings cut by the respective blades.
In the case of a mid-mount lawn tractor having the above rear discharge mower unit according to this invention suspended between front wheels and rear wheels, the grass clippings outlet may have a discharge opening directed to a position between the rear wheels. Then, the grass clippings may be heaped between the ruts of the rear wheels without being crushed under the wheels, thereby to facilitate a subsequent grass collecting operation.
The secondary object of this invention is fulfilled by a lawn tractor having the foregoing rear discharge mower unit suspended between front wheels and rear wheels, a grass catcher disposed rearwardly of the rear wheels, and a grass clippings transport duct having one end connected to the grass clippings outlet, extending between the rear wheels, and having the other end connected to the grass catcher.
In this construction, grass clippings cut by the respective blades and collected in the grass clippings outlet after flowing through the respective flow paths are transported through the grass clippings transport duct to the grass catcher to accumulate therein. Since each flow path is defined by its own baffle, there occurs no loss of air flow, whereby the grass clippings pass through the grass clippings transport duct with sufficient momentum.
A connection between the grass catcher and the grass clippings transport duct is usually located at a higher level than the bottom of the grass catcher. In a preferred embodiment of this invention, the rear wheels have axles downwardly offset in an intermediate portion, and the grass clippings transport duct extends obliquely upward over an offset axle portion. Thus, the grass clippings transport duct extends with a relatively gentle inclination to be connected to a desired connecting position of the grass catcher.
Further, a lawn tractor in a preferred embodiment of this invention may have an engine disposed in a forward position of a tractor body and a propelling transmission disposed in a rearward position of the tractor body. The engine and transmission are interconnected by a transmission shaft extending at one side of a longitudinal axis of the tractor body, while the grass clippings transport duct extends at the other side of the longitudinal axis. With this construction, a limited space under the tractor body is allocated to the transmission shaft and the grass clippings transport duct. This realizes a mid-mount lawn tractor equipped with a grass catcher, which has a compact construction with reduced dead space.
Other features and advantages of this invention will be apparent from the following description of an embodiment of the invention taken with reference to the drawings.